Correct me if I'm wrong, but some words in here seem more Russian than Ukrainian to me. Is this song from a more eastern part of Ukraine? Or given that they're singing about the tsar, from an older form of Ukrainian?

To be honest, I have no idea. Sadly, I neither speak Ukrainian nor understand it, I found this song on YouTube a couple of months ago and I've been very intrigued by its lyrics until today... Maybe Dora can help us with the answer, I am also curious about this now...

It's Ukrainian, for sure, if you listen to it you'll notice it even more clearly, for ex : "Неси та гуляй" (Nessy ta huliay) - btw "та" is typically Ukrainian, it stands for Russian "и". There are variants and many interpretations.

Already the first word is typically Ukrainian : "їхав" (pronounced "yikhav", Russian : ехал, "yekhaL"). There is no more such letter as "ї" (or і) in Russian. And the (past) ending in "-в" instead of Russian "-л". Also "як" for Russian "как", among many other clues.

Yes, їхав is a typical Ukrainian word and also the past form ends in в. Russian ends in л and in Belarussian ỹ (masc) ла (fem), лi (pl). My grandfather is form Donetsk so he speaks perfectly Ukrainian so I ask him to review the text. Ukrainian is closer to Polish and Belarusian, there're only two different letters Ї and Ґ. I don't remember a Russian word with Ї. Russian and Belarusian have a common Slavic basis but Belarusian uses more polish vocabulary. Trayasyanka is Russian with a Belarusian accent and many elements from the Belarusian vocabulary. It is not the same as Belarusian, though. The majority of the population of Belarus nowadays speak Trasyanka.

I never said it was Russian. As a native Russian speaker who also understands Ukrainian, I can tell the difference between them.

But just like in Ukrainian spoken in the western part there are some Polish borrowings, some of the words here seem to be more as they are in Russian than they should be in standard Ukrainian. Could be due to regional variations.

Just a few examples: "лучше/краще" (although both appear), "любить/кохати" (not to mention all the verb infinitives ending in -ь as in Russian as opposed to -и as in Ukrainian), "год/рiк".